Brake bleeding after MC replacement - Conflicting procedures

[peteracs]

Hi

Given the orientation of the bleed screws and the pathway to them, it would be very unusual to have air trapped in them.

If you have already tested the m/c on its own, you must have some blanks to block the ports. Try using them to isolate each circuit in turn to see if you can isolate the problem circuit.

You may find it is just one circuit that is causing the problem.

Peter

[JASPER_40]

Thanks for all the good info Guys......appreciated

Regrettably still not solved the problem and still have a longish pedal travel and spongy brakes.

Since my last update, I have added brand new discs / Pads front and rear at a staggering cost !!!! (These items are enormously expensive in Australia and sourced internationally the cost of shipping is almost prohibitive).  The reason for the expense is that the discs, especially rears had a substantial lip and have been machined by the previous owner to well below minimum thickness. I had previously put new pads in the rear and had noticed that the wear on the pads suggested that the contact area was compromised by the lip....hence the new discs.
The discs will definately improve the efficiency of the brakes and may possibly improve the pedal travel...yet to be tested.

One thing I am getting obsessed with is the rear brake compensator valve....which is also new. I had someone operate the pedal whilst I was watching the compensator action and can see that the plunger / piston moves out about 2 - 3 mm with the action of the pedal......surely this will impact the pedal travel ??
Could be I need to adjust it better so that the resistance offered by the "torsion bar" is far greater such that it doesnt allow the plunger to move when the car is level and unloaded. Not sure how much force the plunger exerts upon braking.

My plan is to bypass the compensator valve altogether using a nifty little bypass connector I got and this will tell me for sure if the compensator action is the issue.

I am hoping that the above fixes will get the brakes into an acceptable operational state such that it will pass an inspection. A lot of me thinks that the young lads in the tester station expect that the brakes should be every bit as as good as a modern car....should they be  ?

The saga continues .....

[SanRemo78]

Have a look at the state of all the bushes in the linkage. The ones on my car were falling apart when I dismantled it and are being replaced with new on the rebuild. If they have failed on your car then that might allow the piston to move as the actuator bar can move within the bushes and cause the symptoms you're seeing? You could eliminate the compensator and it's linkage by removing it and joining the in and out pipe feeds together. If that created a solid pedal you're closer to sorting it?

Guy

[WestonE]

Beta Brakes are respected, were very good in their time and normally good for spirited road use. They should comfortably pass MOT testing standards but are not what you get with current generation German Autobahn designed machinery.   

Eric

[JASPER_40]

Have a look at the state of all the bushes in the linkage. The ones on my car were falling apart when I dismantled it and are being replaced with new on the rebuild. If they have failed on your car then that might allow the piston to move as the actuator bar can move within the bushes and cause the symptoms you're seeing? You could eliminate the compensator and it's linkage by removing it and joining the in and out pipe feeds together. If that created a solid pedal you're closer to sorting it?

Guy

Thanks Guy....yep, I found that too that the bushes disintergrated when I tried to remove them so all have been replaced. even then, the piston / plunger in the compensator still moves a couple of mm when the pedal is pushed. I even tried adjusting the compensator to its max tension and the movement of the plunger under braking is still enough to move it a couple of mm.

I wonder if the PO has moved the connection arm from the sway bar to the compensator torsion bar....and so not allowing enough tension to be applied when the car is level. I am 100% convinced that this plunger movement Must surely affect the pedal travel so I need to engineer this movement out by applying more tension on the torsion bar at the compensator or by elimination altogether.

Regardless, my next move is to introduce the simple compensator bypass pipe to conclusively tell me if the 3mm of plunger movement is enough to cause the longer pedal travel and create the spongy feeling.

[WestonE]

One thought if your car is RHD is to look closely at the cross links and pivots from pedal to servo for excess play. The center of the link is LH and RH threaded to allow play to be adjusted out and the pedal ball joint has a cap that can be adjusted in to remove play.

Enjoy!

Eric
PS the Haynes Beta manual has a description on how to adjust the Bias valve for load.

[JASPER_40]

Beta Brakes are respected, were very good in their time and normally good for spirited road use. They should comfortably pass MOT testing standards but are not what you get with current generation German Autobahn designed machinery.   

Eric

Thanks Eric,

The problem is also that I have nothing to compare this to which has this brake compensator valve. It could be that this is how Lancia beta brakes are supposed to be as I am used to the my German daily driver. (as you said)

I need to put the wheels back on and get this thing on the gound for a road test. I am certain that the new discs/pads will make a massive difference and also the loading of the rear suspension could help the tension on the rear compensator.

watch this space....

[JASPER_40]

One thought if your car is RHD is to look closely at the cross links and pivots from pedal to servo for excess play. The center of the link is LH and RH threaded to allow play to be adjusted out and the pedal ball joint has a cap that can be adjusted in to remove play.

Enjoy!

Eric
PS the Haynes Beta manual has a description on how to adjust the Bias valve for load.

Just to address your questions....I am confident the linkage has no play as I have taken a video of the fluid in the reservoir when I very very lightly touch the brake pedal and the fluid is disturbed suggesting to me that the pistons in the MC are sensitive to movement of the brake pedal.

As for the Haynes manual.....have followed that to the letter.

Maybe I need to get the car on its wheels and allow the suspension to settle to see if it lays lower that how I have the brake compensator set up for......might make a difference. My expectation is that the piston in the compensator should not move at all when he brakes are applied when stopped hence you should get a 50/50 brake distribution. When the nose of the car dips under braking then this is when the piston in the compensator should move to lessen the distribution to the rear.

Will test and report back....

[JohnFol]

Are the banjo bolts 10mx1.25

I spotted a link to this in another thread

https://www.ebay.co.uk/itm/131817736572

If so I might replace these bolts rather than risk snapping the bleed nipples.

[peteracs]

Hi John

There is no down side to trying to loosen off the bleed nipples, if they break, they remain sealed. These banjo bolts are a good solution if you do not want to have the calipers refurbished and one does break.

Normally when I have bought replacement break hoses I have received new banjo bolts and crush washers.

Mark also has these banjo bleed bolts on his site, but current showing as sold out.

In answer yes, M10x1.25, go for stainless ones if you can.

Peter

[Nigel]

When I first approached the brakes on my car, the bleed nipples felt very tight.

I used a plumbers torch to warm the caliper, just around the nipple.
All the nipples came free after that. I then replaced them, adding some copper-slip on
the threads.

I'm not sure the banjo bolt bleed option would get all the air out.

Nigel

[peteracs]

Hi Nigel

Yes the banjo bleed option is not ideal as the bleed nipples are direct from the cylinder, however the orientation of the banjo bolts being at th top of the calipers should allow the oil to fill the cylinder and allow the air to escape.

Peter